1. Field of the Invention
The present invention relates generally to an apparatus for selectively changing the inclination angle of a keyboard during use by an operator, and more particularly, the invention concerns a method and apparatus by which the symptoms of carpal tunnel syndromes and other types of repetitive motion diseases may be reduced.
2. Description of the Related Art
Carpal tunnel syndrome is a condition of the hand which results in pain and discomfort and has been recognized and treated for many years. It is believed that certain occupations cause or aggravate carpal tunnel syndrome (Armstrong, 1983; Armstrong and Chaffin, 1979). Armstrong (1983) called it "one of a family of occupational illnesses". It is said that use of the hand with the wrist in certain static postures causes compression of the median nerve, and that occupations involving prolonged use of such postures can cause or worsen the condition (Armstrong, 1983; Brian et al. 1947; Tanzer, 1959).
To alleviate the effects of carpal tunnel syndrome, often the treatment involves taking anti-inflammatory medications, using wrist braces to restrict motion in the wrist, and, ultimately, surgery on the carpal tunnel. These treatments are directed to the treatment of the condition--not the prevention of its occurrence--and are not entirely satisfactory. Carpal tunnel syndrome occurring after repetitive motion does not generally respond well to the treatments useful for inflammatory or anatomic changes. It is believed that the proposed pathophysiology of the repetitive motion condition combined with prolonged repetitive flexion of the fingers against resistance (i.e., the keyboard) inhibits venous return from the fingers, causing edema within the carpal tunnel. As the compartmentalized edema increases, the hydrostatic pressure likewise increases, compromising the microvasculature of the median nerve. Symptoms of pain, proprioceptive dysfunction and, if left untreated, denervation muscular atrophy occur.
Most of the currently available devices to reduce carpal tunnel syndrome in keyboard operators consist of wrist supports or a padded rest to allow the operator to maintain their wrists in a more relaxed or static position while using the keyboard.
U.S. Pat. No. 4,402,624 to Stahl and Wachs discloses a keyboard that may be made incrementally adjustable between maximum and minimum inclination angles to suit individual operators. The keyboard assembly is adjusted by a hand operated mechanism that alters the inclination of the working face of the keyboard through a range of angles. The adjustment mechanism comprises a cam plate used as a support at the back of a keyboard. The cam plate has variable settings arrived at by rotation of an adjustment shaft, which in turn is operated by a series of gear members driven from a control shaft.
U.S. Pat. No. 4,773,783 to Dickie discloses a keyboard adjusting mechanism that has an attitude adjusting mechanism comprising a shaft extending lengthwise along the rear inside of the case and two legs mounted at the extremities of the shaft. The shaft is indexed to various index positions, which set the attitude of the keyboard.
U.S. Pat. No. 5,101,736 to Bommarito et al. discloses an adjustable desk having among its components a centrally located motorized platform adapted to support a keyboard. The platform may be adjusted over a wide range, and comprises three planar sections stacked on top of each other. The two lower sections are hinged to one another along their front edge, while the top section is slidably connected to the middle section. A motor and threaded screw is coupled to the middle section so that it may be tilted relative to the bottom section, giving the keyboard platform motorized tilt adjustment.
U.S. Pat. No. 5,041,770 to Seiler et al. discloses an apparatus for adjusting a keyboard vertically up and down, or pivotally. The pivotal adjustment mechanism permits the keyboard support to be adjusted about a substantially horizontal axis. These adjusting mechanisms are electrically controlled by the computer user. The disclosure also describes an adjustable wrist support. One object of this invention is to provide relief from repetitive tasks that would cause carpal tunnel syndrome.
U.S. Pat. No. 5,145,270 to Darden discloses a reverse sloped keyboard that allows users to rest their wrists on the adjacent edge of the keyboard while typing. An object of the invention is to avoid carpal tunnel syndrome by having the keys arranged in tiers descending in a stepwise fashion toward the lower rear edge of the keyboard.
There thus exists a need in the workplace to prevent the occurrence of work-related musculoskeletal disorders that are related to performance of the same motions or motion pattern every few seconds for extended periods of time. Keyboards and keyboard supports available today provide only a fixed inclination angle that may be adjusted manually or by electric means prior commencement of operations. These devices do not provide for a means by which an operator may preset the parameters affecting the inclination angle of the keyboard, and have that angle change automatically while the operator is working.